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		<title>three.js webgl - tone mapping</title>
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		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - Tone Mapping<br />
			Battle Damaged Sci-fi Helmet by
			<a href="https://sketchfab.com/theblueturtle_" target="_blank" rel="noopener">theblueturtle_</a><br />
			<a href="https://hdrihaven.com/hdri/?h=venice_sunset" target="_blank" rel="noopener">Venice Sunset</a> by <a href="https://hdrihaven.com/" target="_blank" rel="noopener">HDRI Haven</a>
		</div>

		<!-- Import maps polyfill -->
		<!-- Remove this when import maps will be widely supported -->
		<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';
			import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
			import { GLTFLoader } from 'three/addons/loaders/GLTFLoader.js';
			import { RGBELoader } from 'three/addons/loaders/RGBELoader.js';

			let mesh, renderer, scene, camera, controls;
			let gui, guiExposure = null;

			const params = {
				exposure: 1.0,
				toneMapping: 'ACESFilmic',
				blurriness: 0.3
			};

			const toneMappingOptions = {
				None: THREE.NoToneMapping,
				Linear: THREE.LinearToneMapping,
				Reinhard: THREE.ReinhardToneMapping,
				Cineon: THREE.CineonToneMapping,
				ACESFilmic: THREE.ACESFilmicToneMapping,
				Custom: THREE.CustomToneMapping
			};

			init().catch( function ( err ) {

				console.error( err );

			} );

			async function init() {

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				document.body.appendChild( renderer.domElement );

				renderer.toneMapping = toneMappingOptions[ params.toneMapping ];
				renderer.toneMappingExposure = params.exposure;

				renderer.outputEncoding = THREE.sRGBEncoding;

				// Set CustomToneMapping to Uncharted2
				// source: http://filmicworlds.com/blog/filmic-tonemapping-operators/

				THREE.ShaderChunk.tonemapping_pars_fragment = THREE.ShaderChunk.tonemapping_pars_fragment.replace(
					'vec3 CustomToneMapping( vec3 color ) { return color; }',
					`#define Uncharted2Helper( x ) max( ( ( x * ( 0.15 * x + 0.10 * 0.50 ) + 0.20 * 0.02 ) / ( x * ( 0.15 * x + 0.50 ) + 0.20 * 0.30 ) ) - 0.02 / 0.30, vec3( 0.0 ) )
					float toneMappingWhitePoint = 1.0;
					vec3 CustomToneMapping( vec3 color ) {
						color *= toneMappingExposure;
						return saturate( Uncharted2Helper( color ) / Uncharted2Helper( vec3( toneMappingWhitePoint ) ) );
					}`
				);

				scene = new THREE.Scene();
				scene.backgroundBlurriness = params.blurriness;

				camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 0.25, 20 );
				camera.position.set( - 1.8, 0.6, 2.7 );

				controls = new OrbitControls( camera, renderer.domElement );
				controls.addEventListener( 'change', render ); // use if there is no animation loop
				controls.enableZoom = false;
				controls.enablePan = false;
				controls.target.set( 0, 0, - 0.2 );
				controls.update();

				const rgbeLoader = new RGBELoader()
					.setPath( 'textures/equirectangular/' );

				const gltfLoader = new GLTFLoader().setPath( 'models/gltf/DamagedHelmet/glTF/' );

				const [ texture, gltf ] = await Promise.all( [
					rgbeLoader.loadAsync( 'venice_sunset_1k.hdr' ),
					gltfLoader.loadAsync( 'DamagedHelmet.gltf' ),
				] );

				// environment

				texture.mapping = THREE.EquirectangularReflectionMapping;

				scene.background = texture;
				scene.environment = texture;

				// model

				mesh = gltf.scene.getObjectByName( 'node_damagedHelmet_-6514' );
				scene.add( mesh );

				render();

				window.addEventListener( 'resize', onWindowResize );

				gui = new GUI();

				gui.add( params, 'toneMapping', Object.keys( toneMappingOptions ) )

					.onChange( function () {

						updateGUI();

						renderer.toneMapping = toneMappingOptions[ params.toneMapping ];
						render();

					} );

				gui.add( params, 'blurriness', 0, 1 )

					.onChange( function ( value ) {

						scene.backgroundBlurriness = value;
						render();

					} );

				updateGUI();

				gui.open();

			}

			function updateGUI() {

				if ( guiExposure !== null ) {

					guiExposure.destroy();
					guiExposure = null;

				}

				if ( params.toneMapping !== 'None' ) {

					guiExposure = gui.add( params, 'exposure', 0, 2 )

						.onChange( function () {

							renderer.toneMappingExposure = params.exposure;
							render();

						} );

				}

			}

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;

				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

				render();

			}

			function render() {

				renderer.render( scene, camera );

			}

		</script>

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